Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th September 2011, 06:15 PM   #31
diyAudio Member
 
Frank Berry's Avatar
 
Join Date: Sep 2003
Location: Midland, Michigan
Quote:
Originally Posted by darkfenriz View Post
The common mode range of such circuits is very limited. They are not intended to work with fully floating signals.
Practically they are only good for ground loop eliminators or so-called DI-boxes, where all signals are referenced to different ground potentials.
Sorry darkrenriz. You are completely wrong.
Opamps have been used for decades as balanced microphone and line level input stages.
They perform very well when driven by floating, balanced audio signals.
__________________
Frank
  Reply With Quote
Old 27th September 2011, 06:32 PM   #32
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
Sort of. If you connect a microphone to such an input stage it will perform flawlessly, but the microphone isn't perfectly floating anymore.
Connect one microphone to several such stages placed in several physically distant locations (which is I believe a merit of this very thread) referenced to different "grounds" or lack of them and you get a nice mess.
  Reply With Quote
Old 27th September 2011, 06:36 PM   #33
diyAudio Member
 
Frank Berry's Avatar
 
Join Date: Sep 2003
Location: Midland, Michigan
I think it's still worth a try. It may not work well with long lines.
Obviously, a transformer on the receive end would solve the problem but that is not an option.
__________________
Frank
  Reply With Quote
Old 27th September 2011, 06:48 PM   #34
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
Yes, galvanic isolation is the safest way, tranformer being the simpliest and generally best way to do it.
Optocoupler working on the discrete representation of the signal, which I suggested is second best.
Differential amplifier solution is fine as long as the common mode range of "floating" is within some limits. Period.
  Reply With Quote
Old 27th September 2011, 09:36 PM   #35
Zaaphod is offline Zaaphod  United States
diyAudio Member
 
Join Date: Aug 2011
Location: Florida
Quote:
Originally Posted by darkfenriz View Post
I'd strongly recommend using more powerfull diodes, perfectly schottky ones like 1N5822

P.S. Have you had a look at TC4422 driver? It seems better.
Thanks for the commendation on the diodes, do you think I should use these just on the output and keep the smaller 1N4148s on the input?

I did not see the TC4422, looks like it would be worth a try. I had a look at the data sheet, the description at the top states power supply of 20V but then the charts list max power supply of 18V... strange


Quote:
Sort of. If you connect a microphone to such an input stage it will perform flawlessly, but the microphone isn't perfectly floating anymore.
Connect one microphone to several such stages placed in several physically distant locations (which is I believe a merit of this very thread) referenced to different "grounds" or lack of them and you get a nice mess.
If all the receivers were powered by floating power supplies, wouldn't the signal on the line still be floating?

Yes, my intention with this project is to send a balanced signal down a long run of UTP cable, and have many receivers along the way. I am trying to create something like a central audio system, that extends to outdoors and into other buildings as well. since I want many receivers, I am trying to keep the cost down per receiver.. When you start multiplying, costs go up fast. which is another reason I like the PWM method, the cost per unit will be fairly low.

For the indoor part, I may still use the analog signal, but the runs will be short, and if I can't get something simple to work, I can use small audio transformers, there won't be anywhere near as many indoor units as outdoor.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
headphone to car amp which takes balanced differential signal, please review circuit emit Car Audio 2 23rd August 2011 05:35 PM
Volume control of a differential signal berni8k Digital Line Level 20 26th August 2009 09:43 AM
Signal Chain, connecting units that each have floating supplies? HankMcSpank Solid State 6 27th December 2008 10:30 PM
Creating a differential signal from a single-ended signal for bridged amps Peter Daniel Chip Amps 45 8th November 2004 12:47 PM


New To Site? Need Help?

All times are GMT. The time now is 05:08 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2